Re: [PATCH] [PATCH v2] perf: Modify MAX_NR_CPUS and MAX_CACHES

From: Jiri Olsa
Date: Wed Jul 17 2019 - 03:30:39 EST

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On Fri, Jun 28, 2019 at 10:35:55AM -0500, Kyle Meyer wrote:
> Perf surpasses the limit of MAX_NR_CPUS and MAX_CACHES while attempting to
> profile 1024 or more CPUs. Increase and/or make each limit dynamic to
> regain normal functionality.
>
> Before:
> perf record -a
> [ perf record: Woken up X times to write data ]
> way too many cpu caches..
> [ perf record: Captured and wrote X MB perf.data (X samples) ]
>
> perf report -C 1024
> Error: failed to set cpu bitmap
> Requested CPU 1024 too large. Consider raising MAX_NR_CPUS
>
> After:
> perf record -a
> [ perf record: Woken up X times to write data ]
> [ perf record: Captured and wrote X MB perf.data (X samples) ]
>
> perf report -C 1024
> ...
>
> The variables nr_cpus_onln and max_caches are alternatives for MAX_NR_CPUS
> and MAX_CACHES, they are initialized at runtime. MAX_NR_CPUS is increased
> from 1024 to 2048 as it is still used by DECLARE_BITMAP() at compile time,
> nr_cpus_onln replaces it elsewhere throughout perf.

I overlooked this one and it no longer applies because of
another change from you:
9f94c7f947e9 perf tools: Increase MAX_NR_CPUS and MAX_CACHES

my worry here (did not check completely) is that some paths you
changed can't use number of cpus from sysconf(_SC_NPROCESSORS_ONLN),
because they are within the report code path, and the data can come
from another machine with different number of cpus

jirka

>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: Russ Anderson <russ.anderson@xxxxxxx>
> Signed-off-by: Kyle Meyer <kyle.meyer@xxxxxxx>
> ---
> tools/perf/perf.c | 6 ++++++
> tools/perf/perf.h | 3 ++-
> tools/perf/util/cpumap.c | 6 +++---
> tools/perf/util/header.c | 7 +++----
> tools/perf/util/machine.c | 11 +++++------
> tools/perf/util/session.c | 5 ++---
> tools/perf/util/stat.c | 4 ++--
> tools/perf/util/svghelper.c | 10 +++++-----
> 8 files changed, 28 insertions(+), 24 deletions(-)
>
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index 72df4b6fa36f..c2c22476a65f 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
> @@ -427,6 +427,12 @@ int main(int argc, const char **argv)
> const char *cmd;
> char sbuf[STRERR_BUFSIZE];
>
> + nr_cpus_onln = sysconf(_SC_NPROCESSORS_ONLN);
> + if (nr_cpus_onln < 0) {
> + fprintf(stderr, "Cannot determine the number of CPUs currently online.\n");
> + goto out;
> + }
> +
> /* libsubcmd init */
> exec_cmd_init("perf", PREFIX, PERF_EXEC_PATH, EXEC_PATH_ENVIRONMENT);
> pager_init(PERF_PAGER_ENVIRONMENT);
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 711e009381ec..603391cac85b 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -26,9 +26,10 @@ static inline unsigned long long rdclock(void)
> }
>
> #ifndef MAX_NR_CPUS
> -#define MAX_NR_CPUS 1024
> +#define MAX_NR_CPUS 2048
> #endif
>
> +int nr_cpus_onln;
> extern const char *input_name;
> extern bool perf_host, perf_guest;
> extern const char perf_version_string[];
> diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> index c11a459ca582..83c05afef063 100644
> --- a/tools/perf/util/cpumap.c
> +++ b/tools/perf/util/cpumap.c
> @@ -72,7 +72,7 @@ struct cpu_map *cpu_map__read(FILE *file)
> int new_max = nr_cpus + cpu - prev - 1;
>
> if (new_max >= max_entries) {
> - max_entries = new_max + MAX_NR_CPUS / 2;
> + max_entries = new_max + nr_cpus_onln / 2;
> tmp = realloc(tmp_cpus, max_entries * sizeof(int));
> if (tmp == NULL)
> goto out_free_tmp;
> @@ -83,7 +83,7 @@ struct cpu_map *cpu_map__read(FILE *file)
> tmp_cpus[nr_cpus++] = prev;
> }
> if (nr_cpus == max_entries) {
> - max_entries += MAX_NR_CPUS;
> + max_entries += nr_cpus_onln;
> tmp = realloc(tmp_cpus, max_entries * sizeof(int));
> if (tmp == NULL)
> goto out_free_tmp;
> @@ -170,7 +170,7 @@ struct cpu_map *cpu_map__new(const char *cpu_list)
> goto invalid;
>
> if (nr_cpus == max_entries) {
> - max_entries += MAX_NR_CPUS;
> + max_entries += nr_cpus_onln;
> tmp = realloc(tmp_cpus, max_entries * sizeof(int));
> if (tmp == NULL)
> goto invalid;
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 06ddb6618ef3..78f1acb069ed 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1121,16 +1121,15 @@ static int build_caches(struct cpu_cache_level caches[], u32 size, u32 *cntp)
> return 0;
> }
>
> -#define MAX_CACHES 2000
> -
> static int write_cache(struct feat_fd *ff,
> struct perf_evlist *evlist __maybe_unused)
> {
> - struct cpu_cache_level caches[MAX_CACHES];
> + u32 max_caches = (nr_cpus_onln * 4);
> + struct cpu_cache_level caches[max_caches];
> u32 cnt = 0, i, version = 1;
> int ret;
>
> - ret = build_caches(caches, MAX_CACHES, &cnt);
> + ret = build_caches(caches, max_caches, &cnt);
> if (ret)
> goto out;
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 17eec39e775e..b4d792dbeb1f 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -2593,7 +2593,7 @@ int __machine__synthesize_threads(struct machine *machine, struct perf_tool *too
>
> pid_t machine__get_current_tid(struct machine *machine, int cpu)
> {
> - if (cpu < 0 || cpu >= MAX_NR_CPUS || !machine->current_tid)
> + if (cpu < 0 || cpu >= nr_cpus_onln || !machine->current_tid)
> return -1;
>
> return machine->current_tid[cpu];
> @@ -2610,16 +2610,15 @@ int machine__set_current_tid(struct machine *machine, int cpu, pid_t pid,
> if (!machine->current_tid) {
> int i;
>
> - machine->current_tid = calloc(MAX_NR_CPUS, sizeof(pid_t));
> + machine->current_tid = calloc(nr_cpus_onln, sizeof(pid_t));
> if (!machine->current_tid)
> return -ENOMEM;
> - for (i = 0; i < MAX_NR_CPUS; i++)
> + for (i = 0; i < nr_cpus_onln; i++)
> machine->current_tid[i] = -1;
> }
>
> - if (cpu >= MAX_NR_CPUS) {
> - pr_err("Requested CPU %d too large. ", cpu);
> - pr_err("Consider raising MAX_NR_CPUS\n");
> + if (cpu >= nr_cpus_onln) {
> + pr_err("Requested CPU %d too large, there are %d CPUs currently online.\n", cpu, nr_cpus_onln);
> return -EINVAL;
> }
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 54cf163347f7..8641364555fb 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2289,9 +2289,8 @@ int perf_session__cpu_bitmap(struct perf_session *session,
> for (i = 0; i < map->nr; i++) {
> int cpu = map->map[i];
>
> - if (cpu >= MAX_NR_CPUS) {
> - pr_err("Requested CPU %d too large. "
> - "Consider raising MAX_NR_CPUS\n", cpu);
> + if (cpu >= nr_cpus_onln) {
> + pr_err("Requested CPU %d too large, there are %d CPUs currently online.\n", cpu, nr_cpus_onln);
> goto out_delete_map;
> }
>
> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> index d91fe754b6d2..9d4a3b96496a 100644
> --- a/tools/perf/util/stat.c
> +++ b/tools/perf/util/stat.c
> @@ -207,7 +207,7 @@ void perf_evlist__reset_stats(struct perf_evlist *evlist)
> static void zero_per_pkg(struct perf_evsel *counter)
> {
> if (counter->per_pkg_mask)
> - memset(counter->per_pkg_mask, 0, MAX_NR_CPUS);
> + memset(counter->per_pkg_mask, 0, nr_cpus_onln);
> }
>
> static int check_per_pkg(struct perf_evsel *counter,
> @@ -226,7 +226,7 @@ static int check_per_pkg(struct perf_evsel *counter,
> return 0;
>
> if (!mask) {
> - mask = zalloc(MAX_NR_CPUS);
> + mask = zalloc(nr_cpus_onln);
> if (!mask)
> return -ENOMEM;
>
> diff --git a/tools/perf/util/svghelper.c b/tools/perf/util/svghelper.c
> index fab8a048d31b..6a8241932dce 100644
> --- a/tools/perf/util/svghelper.c
> +++ b/tools/perf/util/svghelper.c
> @@ -705,7 +705,7 @@ static void scan_thread_topology(int *map, struct topology *t, int cpu, int *pos
>
> for_each_set_bit(thr,
> cpumask_bits(&t->sib_thr[i]),
> - MAX_NR_CPUS)
> + nr_cpus_onln)
> if (map[thr] == -1)
> map[thr] = (*pos)++;
> }
> @@ -720,7 +720,7 @@ static void scan_core_topology(int *map, struct topology *t)
> for (i = 0; i < t->sib_core_nr; i++)
> for_each_set_bit(cpu,
> cpumask_bits(&t->sib_core[i]),
> - MAX_NR_CPUS)
> + nr_cpus_onln)
> scan_thread_topology(map, t, cpu, &pos);
> }
>
> @@ -737,7 +737,7 @@ static int str_to_bitmap(char *s, cpumask_t *b)
>
> for (i = 0; i < m->nr; i++) {
> c = m->map[i];
> - if (c >= MAX_NR_CPUS) {
> + if (c >= nr_cpus_onln) {
> ret = -1;
> break;
> }
> @@ -784,13 +784,13 @@ int svg_build_topology_map(char *sib_core, int sib_core_nr,
> sib_thr += strlen(sib_thr) + 1;
> }
>
> - topology_map = malloc(sizeof(int) * MAX_NR_CPUS);
> + topology_map = malloc(sizeof(int) * nr_cpus_onln);
> if (!topology_map) {
> fprintf(stderr, "topology: no memory\n");
> goto exit;
> }
>
> - for (i = 0; i < MAX_NR_CPUS; i++)
> + for (i = 0; i < nr_cpus_onln; i++)
> topology_map[i] = -1;
>
> scan_core_topology(topology_map, &t);
> --
> 2.12.3
>

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